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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING 200 watt emergency power supply from a 12 volt battery. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Power Supplies Recently, due to the unsatisfactory economic situation in the country, power cuts have become more frequent. In dacha cooperatives, even in the best of times, emergency shutdowns occurred frequently. The voltage converter, which is described below, allows you to power electrical appliances from a 12 V battery. The duration of power supply in emergency mode is determined by the capacity of the battery and can be up to several hours. The total power of consumers should not exceed 200 watts. Voltage shape - rectangular pulses, frequency - 50 Hz. Consider the operation of an emergency power supply device, or voltage converter, according to its schematic diagram, shown in fig. 146. On the logic elements DD1.1 - DD1.3 of the DD1 microcircuit, a generator is made that generates rectangular pulses with a frequency of 100 Hz. Through the buffer element DD1.4, the pulses are fed to the counting input C of the JK flip-flop DD2. To ensure the counting mode of operation, a logic 1 voltage is applied to the information inputs J and K of the trigger, and a logic 0 voltage is applied to the installation inputs R and S. On the direct and inverse outputs of the trigger, the pulses follow at a frequency of 50 Hz, and the phases of the pulses are opposite (differ by 180 °). The need to use a trigger is due to the fact that at its outputs the pulses have the shape of an ideal meander, i.e. absolutely symmetrical (duty ratio is 2).
From the trigger outputs, the pulses are fed to the buffer logic elements DD1.5, DD1.6, which amplify the current pulses, and then fed through the resistors R3, R6 to the bases of the transistors VT1, VT2. The collector circuits of these transistors include half of the winding I of the transformer T1. From the windings II, III of the transformer T1, rectangular pulses are fed to the bases of transistors VT3, VT4. These transistors, operating in the key mode, alternately supply voltage to the halves of the winding I of the transformer T1. The half-windings of the transformer are included in the emitter circuits of the transistors, and not in the collector circuits; this is done so that transistors VT3, VT4 of the P210Sh type, in which a collector is connected to the case, could be installed on one radiator without electrical insulation of the transistor cases. It should be noted that in this case, the half-windings of the transformer T1 could equally well (from the point of view of circuitry) be included in the collector circuits of transistors. From the winding II of the transformer T2, a voltage of 220 V with a frequency of 50 Hz is removed, which is used to power electrical appliances. The difference in the voltage form from the sinusoidal practically does not affect the operation of electrical appliances. The transformation ratio of the transformer T2 (the ratio of the number of turns of the winding II and half of the winding I) is 220/12 = 18,3. LED HL1 indicates the presence of high voltage on the secondary winding of the transformer T2. Diode VD2 protects the LED from being exposed to reverse voltage. The microcircuits are powered by a parametric voltage regulator, made on the zener diode VD1 and resistor R7. Voltage stabilization is necessary in order to ensure that the frequency of the generator does not change when the battery voltage changes. Capacitor C3 smooths out the 50 Hz voltage ripple. Capacitor C2 shunts high-frequency random noise. About device details. Instead of microcircuits of the K561 series, microcircuits of the 564, KR1561 series can be used. Transistors VT1, VT2 can be any of the KT815, KT817, KT630 series; VT3, VT4 - P210 with any letters, as well as 1T806, GT806, 1T813 with any letter indices. The use of silicon transistors as VT3, VT4 is undesirable, since they are characterized by a larger voltage drop across junctions in the saturation state than that of germanium, which leads to significant thermal losses and reduces the efficiency of the device. We will replace the VD1 zener diode with D814B, however, its temperature stability of the voltage is somewhat lower. Diode VD2 can be absolutely anything. Capacitor C1 must have a small temperature coefficient of capacitance, since the stability of the generator frequency depends on it. This condition is satisfied by capacitors of types K73-17, K73-24. Capacitor C2 - type KLS, K10-7V, KM-5, KM-6. Oxide capacitor C3 - K50-16, K50-24, K50-35. Trimmer resistor R2 - type SP5-2, SPZ-14; the remaining resistors are C1-12, C2-23 or MLT. Switch Q1 - toggle switch type TV 1-4 with four groups of closing contacts; to increase the switching current, all four groups are connected in parallel. Nest XS1 - type RD1. Transformer T1 is made on a tape magnetic circuit SHL 12x20. Winding I contains 500 turns of wire PEV-2 0,21 with a tap from the middle; windings II and III - 30 turns of wire PEV-2 0,4 each. The outputs of the windings II and III of the same name must be marked (shown as dots in the diagram). Transformer T2 is made on the magnetic circuit ShL32x32. Its winding I contains 96 turns of PEV-2 2,5 wire with a tap from the middle; winding II - 920 turns of wire PEV-2 0,56 As a GB1 battery, a 12 V starter car battery, for example, 6ST60, can be used. The capacity of this battery determines the time of continuous operation of the converter on the load. The design of the device is arbitrary. Transistors VT3, VT4 must be installed on a heat sink with an area of about 200 cm ^ 2. The circuits connecting the battery, power transistors, transformer T2, must be made with wires with a cross section of at least 4 mm ^ 2. Setting up the device consists in setting the generator frequency to 2 Hz using a tuned resistor R100. Publication: cxem.net
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